[Haskell-cafe] NB: DO NOT USE `pure = return`

Dear Cafe, the migration guide (for AMP) https://gitlab.haskell.org/ghc/ghc/wikis/migration/7.10#ghc-says-no-instance... contains this advice: instance Applicative Foo where -- NB: DO NOT USE `pure = return` Why not? Because it would require another refactoring once "monad of no return" comes true? So defining `return` in the Monad instance should work fine until then? Which is when exactly? I can't quite make it out from https://gitlab.haskell.org/ghc/ghc/wikis/proposal/monad-of-no-return/discuss... - J.W.